-LRB- CNN -RRB- -- Sudan has arrested foreigners in the disputed region of Heglig , its defense ministry said Saturday , the latest in the spiraling conflict between the Sudans .

Those arrested were identified by the defense ministry as British , Norwegian , South African and South Sudanese .

`` They were engaged in suspicious activities , collecting war debris , '' it said .

Meanwhile , a South Sudanese military spokesman reported ongoing clashes and bombings -- though a Sudanese military spokesman denied any such attacks .

Col. Philip Aguer , a spokesman for the Sudan People 's Liberation Army of South Sudan , said eight bombs were dropped in Unity state Saturday .

Friday , `` Khartoum-supported mercenaries '' attacked an SPLA position in a town called Wau , causing 21 deaths , he said . Three fighters were captured alive , he added .

The SPLA seized three trucks , which are said to belong to the Sudanese Armed Forces , said Aguer , vowing to retaliate against `` all these acts of aggression . ''

But Al-Sawarmi Khalid , a spokesman for the Sudanese Armed Forces , said , `` We have not bombed Wau , or any other place in South Sudan . ''

South Sudan split from Sudan last year as part of a 2005 peace deal that ended decades of war in Africa 's largest nation . The war left 2 million people dead and ended with the peace agreement that included an independence referendum for the south .

Despite the split in July , unresolved issues remain between the two , including status of their citizens , division of national debt , disputed border areas and sharing of oil wealth .

Simmering tensions peaked this month when South Sudan seized the oil-producing region of Heglig from Sudan , raising the stakes by targeting a resource that fuels the economies of both nations .

Heglig oil facilities account for about half of Sudan 's production of 115,000 barrels a day .

Sudan claims ownership for the region , and lodged complaints with the United Nations and the African Union to pressure South Sudan to withdraw troops from its territory .

A day after South Sudan withdrew from the disputed region , it accused Sudan of launching ground and aerial attacks on its territory .

CNN 's Kim Chakanetsa and journalist Isma'il Kushkush contributed to this report .

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Those arrested are British , Norweigan , South Afrian and South Sudanese

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`` They were engaged in suspicious activities , collecting war debris , '' it says

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A South Sudanese military spokesman reports ongoing clashes and bombings

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A Sudanese spokesman says its military did n't carry out any attacks in South Sudan